Horn antenna having reduced length



Dec. 11, 1962 B. G. HAGAMAN 3,068,478

HORN ANTENNA HAVING REDUCED LENGTH TZLEILE' v A Tlta/z fu, 32

ATTO R N EYS United States Patent Oil-ice y 3,068,478 Patented Dec. 11,1962 3 068,478 HORN ANTENNA HVIN G REDUCED LENGTH Boynton G. I-Iagamau,Falls Church, Va., assiguor to Antenna Systems, Inc., Washington, D.C.,a corporation of Delaware Filed Aug. 24, 1959, Ser. No. 835,666 Claims.(Cl. 343-756) The present invention relates to electromagnetic hornantennas and particularly to means and methods of reducing the length ofhorn antennas.

According to the present invention the length of a horn antenna can bereduced considerably. This is accomplished by exciting the horn by anarray of radiators disposed in the wave guide connected to the horn sothat at a point thereof which would normally be, say, about the middleof the length of the horn, a desirable wave front is produced. Thus, ata point not too far from the aperture of the horn, the wave front nearthe walls of the horn is not delayed relative to the portion thereofnear the middle of the horn, as it would be in a conventional hornantenna. If desired the array of radiators may be energized in phase sothat a plain wave front occurs at the point of excitation. Thus, thewave will arrive at the aperture at or nearly in phase, thereby enablingthe antenna to maintain a high radiation eiliciency.

An object of the present invention is to accomplish this result withoutimpairing or obstructing the transmission of waves through the horn.

Other objects and advantages of the invention will become apparent andthe invention itself will be fully understood from the followingdescription and the drawing, in which:

FIG. 1 is a front view looking into the aperture of a horn antennaaccording to the invention;

FIG. 2 is a side view of the antenna shown in FIG. l; and

FIG. 3 is a side view of another embodiment of my invention.

FIGS. 1 and 2 show the invention applied to a horn antenna of the typedisclosed in my copending application Serial No. 791,248, now Patent No.2,992,429. The antenna has a rectangular tapered aperture with thediagonals of the rectangular aperture extending vertically andhorizontally. It will be assumed that the antenna is to be used forreceiving or transmitting horizontally polarized waves although it willbe readily understood that the invention can be used for verticallypolarized waves merely by changing its orientation by 90. The horn isformed of eight triangular sides 11-18 which dene a rectangular orsquare aperture 20. It will be understood that other kinds of taperedhorns may be used, several types of which are disclosed in my priorPatent 2,851,686. At the small end 21 of the horn there is connected arectangular wave guide 22. The wave guide is divided into a plurality ofcells by metallic partitions 24 and 26. In each cell 25 a horizontallinear radiator 28 is mounted. Radiators 28 may be any suitable type ofantennas such as, for example, linear probes mounted on, but insulatedfrom the metallic partitions 24 and the end wall 30 of the wave guide.It will be evident that other types of well-known linear radiators suchas dipoles, for example, could be used. Radiators 28 are connected bytransmission lines 30 to suitable radio receiving or transmittingequipment 32. The transmission lines 30 conveniently can be coaxialtransmission lines. The transmission lines are preferably arranged sothat radiators 28 are connected to the translating apparatus 32 in thesame phase. Thus, if the translating apparatus 32 is a transmitter, theradiators 28 will be excited in phase and produce a plane wave front inthe plane of the radiators. This plane wave is then propagated throughwave guide 22 and the horn to the radiating aperture 20. Since the hornis comparatively short, the `amount of dephasing which occurs in thetravel of the wave to the aperture is relatively small, so that even ashort horn lengtha'nd large llare angle does not cause an excessivephase diierence of the energy at the radiating aperture 20. As a result,the operating eiciency and the directivity of the horn remains largedespite the short length of the horn antenna.

FIG. 3 shows an arrangement similar to that of FIGS. 1 and 2 except thatthe horn 40 is of a conventional flared rectangular type, rather thanthe tapered aperture type shown in FIGS. l and 2.

If desired, the radiators 28 can be energized, as disclosed in mycopending application, Serial No. 835,730, led August 24, 1959. When soenergized, the radiators in the cells at the middle of the wave guideare excited with waves having a phase delay relative to the wavesupplied to the radiators near the end walls of the wave guide. In thisway, the longer time of travel of the wave from the outermost radiatorsmay be compensated. Such phase delay may be provided by suitable delaylines or delay devices or by additional length of the transmission tlines connected to the radiators in the middle cells of the wave guide.

Many modications and variations of the invention herein illustrated willbe apparent to those skilled in the art and therefore the invention isnot to be construed as limited except as defined in the followingclaims.

What is claimed is:

1. A shortened horn antenna having a plurality of outwardly flaredperipheral walls joined to one another along their longitudinal edgesand dening a single radiating f aperture, a rectangular wave guideconnected directly to all said walls at the small end of the horn,intersecting metallic partitions in said wave guide extendingthereacross in a direction substantially parallel to the axis of thehorn and dividing the wave guide into a plurality of cells, atwo-dimensional array of aligned radiators mounted in said cells of thewave guide, and radio Wave transmission means connected to all of saidradiators.

2. A shortened horn antenna comprising a flared electromagnetic hornhaving a single radiating aperature at one end and an opening at theother end, a rectangular wave guide connected to the other end of thehorn, metallic, mutually perpendicular partitions in said wave guideextending thereacross in a direction substantially parallel to the axisof the horn and dividing the wave guide into a rectangular array ofcells, a two-dimensional rectangular array of linear parallel radiatorsmounted in said cells of the wave guide and transmission line meansconnected to all of said radiators.

3. A shortened horn antenna comprising a flared horn, ya wave guideconnected to .the small end of the horn, intersecting metallicpartitions wholly within said wave guide extending parallel to the axisof the horn and dividing the wave guide into a plurality of cells, atwo-dimensional array of radiators mounted in said cells of the waveguide, and transmission means connected to all of said radiators forenergizing a plurality of said radiators out of phase with otherradiators.

4. A shortened horn antenna comprising a wave guide connected to thesmall end of the horn, intersecting metallic partitions in said waveguide extending thereacross parallel to the axis of the horn anddividing the wave guide into a plurality of cells, a two-dimensionalarray of parallel linear polarization radiators mounted in said cells ofthe wave guide, and wave translation means connected to all of saidradiators.

5. A shortened horn antenna comprising a flared horn having plane wallsforming a single aperture having a maximum width at the middle thereofand tapering to a-minimum value at the ends thereof, a rectangular waveguide connected to the small end of the horn, metallic, mutuallyperpendicular partitions in said wave guide extending thereacrossparallel to the axis of the horn and dividing the wave guide into arectangular array of cells, a 4two-dimensional rectangular array oflinear parallel radiators mounted in said cells of the wave guide andtransmission line means connected to al1 of said radiators forenergizing said radiators with radio waves having the same phase.

References Cited in the tile of this patent UNITED STATES PATENTS

